Milwaukee Sheriff David A. Clarke, hearing today that among the president’s executive actions to prevent gun violence is to hire more FBI agents to perform background checks on gun buyers, notes that the FBI “dropped the ball” on Dylann Roof, who is accused to killing nine people inside the Emanuel AME Church in Charleston, S.C.

The FBI even admitted that an error on its part contributed to Roof’s ability to purchase a gun legally. The New York Times reported, “Despite new procedures and billions of dollars that have been spent on computer upgrades in the years after the Sept. 11, 2001, terrorist attacks, the federal authorities still do not have a seamless way of examining Americans’ criminal histories that eliminates human error.”